MESOSCALE DISCUSSION 2592
   NWS STORM PREDICTION CENTER NORMAN OK
   0701 AM CST THU DEC 30 2004
   
   AREAS AFFECTED...CENTRAL/NRN SIERRA MTNS AND FAR NRN MTNS OF CA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 301301Z - 301700Z
   
   VERY HEAVY SNOW...WITH RATES OF 2"/HR...EXPECTED ACROSS THE CENTRAL
   SIERRA MTNS THROUGH 18Z WITH SNOW LEVELS HOLDING AROUND 4000 FT.
   SNOW WILL BECOME INTERMITTENT AND SHOWERY ACROSS THE MTNS OF FAR NRN
   CA WITH SNOW LEVELS DROPPING TO 2500 FT BY 18Z.
   
   AT 1230Z...MOSAIC RADAR IMAGERY SHOWS THE PRIMARY FRONTAL
   PRECIPITATION BAND EXTENDING FROM SFO NEWD TO BLU AND INTO THE NRN
   SIERRA MTNS...WITH EMBEDDED CONVECTIVE PRECIPITATION ASSOCIATED WITH
   STEEP MID-LEVEL LAPSE RATES. MODERATE TO HVY SNOW HAS BEEN OBSERVED
   AT BLUE CANYON SINCE 0530Z. VERY STRONG WLY TO SWLY FLOW IS EVIDENT
   ON 12Z OAK SOUNDING...WITH 50KTS AT 700MB AND 90KTS AT 500MB. DEEP
   LAYER SATURATION AND PRECIPITABLE WATER AROUND 0.75" SUGGEST
   CONTINUED STRONG AND MOIST UPSLOPE FLOW...PROPAGATING SLOWLY SWD
   INTO THE CENTRAL SIERRA MTNS THROUGH 18Z. SNOW RATES OF 2"/HR APPEAR
   LIKELY WITH THIS PRIMARY AXIS OF PRECIPITATION INTO EARLY
   AFTERNOON...WITH SNOW LEVELS HOLDING AROUND 4000 FT PER RUC FORECAST
   SOUNDINGS.
   
   PRECIPITATION SHOULD BECOME LIGHTER AND MORE SHOWERY ACROSS THE MTNS
   OF FAR NRN CA AS COLD ADVECTION REGIME ADVECTS INLAND BEHIND PRIMARY
   PRECIPITATION BAND. RUC SOUNDINGS BY 18Z INDICATE SNOW LEVELS AS LOW
   AS 2500FT IN MT SHASTA VICINITY WITH SOME MINIMAL CAPE AROUND 100
   J/KG WHICH WILL BE CONDUCIVE FOR CONVECTIVE SNOW SHOWERS AND
   CONTINUED ISOLATED LIGHTNING STRIKES IN VICINITY OF THE COASTAL
   RANGES. DESPITE OVERALL DECREASING SNOW RATES...BURSTS OF HEAVY SNOW
   WILL REMAIN POSSIBLE THROUGH 18Z ASSOCIATED WITH LOW-TOPPED
   CONVECTIVE CELLS.
   
   ..BANACOS.. 12/30/2004
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A 
   SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 00-01 UTC...
   06-07 UTC...12-13 UTC...AND 18-19 UTC AS SIGNIFICANT SHORT
   RANGE WINTER WEATHER EVENTS UNFOLD.  THIS SCHEDULE WILL BE
   USED FROM DECEMBER 1 THROUGH FEBRUARY 28.
   
   ATTN...WFO...REV...HNX...MFR...STO...EKA...
   
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   38751994 39752029 40802077 41382112 41752138 41882200
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   41172226 41102191 40842167